The effects of two differentiating factors, gamma-IFN and NGF, alone and in combination, on the neuroblastoma clonal cell line, SY5Y, have been characterized. Fourteen neuronal cell marker Abs have been tested on this cell line by immunoperoxidase method, and with three of them the experiments have been completed. The data were presented at the 1991 World Congress on Cell and Tissue Culture, Anaheim, CA, 1991.